With mobile phones being popular and their function being diversified, mobile phones with an automatic focusing camera will better market prospects. Existing mobile phones with automatic focusing cameras usually use electromagnetic induction motors, which have advantages of high rotating speed and high efficiency, but also have disadvantages of poor positioning accuracy, being incapable of fast self-lock, difficult to miniaturize further, so they are not suitable for the trend of making the cameras of mobile phone smaller.
Voice coil motors can support lens to move smoothly and continuously over a small distance. With advantages of small volume and simple structure, the VCM has become widely used in lens modules of mobile phone. However, in a voice coil motor, the lens holder depends on a spring for support, and to keep its position, a continuous electric current is required to obtain an electromagnetic force balancing the force of the spring to keep the position of the lens during shooting of a photo. As the elastic strength of the spring is low, it will vibrate near the target position during positioning, so it is not a good solution for fast positioning required by modern automatic focusing camera systems.